This invention relates to a method of inserting drainage equipment into the ground, in which the soil is drilled with drilling rods having slits distributed along the rod wall so that the said rods, which are left in the ground when the required depth has been reached, also act as drainage pipes. The invention also relates to devices for the implementation of the said method, consisting of drainage pipes which present a number of slits for water drainage, are fitted at the tip with a disposable bit, and are equipped with means designed to prevent clogging of the said slits during drilling, the said means being constituted by a protective sheath made of water-soluble material which dissolves on contact with the water present in the soil.
In accordance with a preferred form of embodiment, the drilling rods are constituted by two coaxial pipes, an outer pipe made of steel and an inner pipe made of plastic, particularly PVC.
The necessary resistance to stresses during drilling is therefore guaranteed by the outer steel pipe, while the long life of the device is ensured by the presence of the inner plastic pipe, which remains in pristine condition for many years.
In accordance with the present state of the art, pipes made of plastic, particularly PVC, containing special slits and covered with a geotextile fabric, are used for soil drainage.
In order to lay these pipes, the soil is drilled with a bit which pulls a metal lining pipe with it as it advances.
When the required depth is reached, the drilling rods are removed, leaving the metal pipe in the ground, and the PVC drainage pipe is inserted inside it.
The outer metal pipe is then removed and the PVC pipe remains in the ground, at the required depth, thus allowing water drainage. As will be seen, this is a rather laborious method which requires time, skilled labour, and the use of expensive, sophisticated equipment for lengthy periods.
It would be desirable to have simpler, faster and cheaper equipment to achieve the same result, and this invention consequently proposes a method and the associated devices in which drilling is performed with rods containing slits which can therefore act directly as drainage pipes, the said rods being left in the ground when the required depth has been reached.
The rods in accordance with the invention are covered with an outer sheath made of water-soluble material, which prevents debris from clogging the drainage slits during excavation and dissolves in a few hours after the pipe comes into contact with the wet soil.